The present invention relates to telecommunication systems, and more particularly, to arrangements for substituting one communication path for another in such systems.
The establishment and control of communication paths is the very basis of providing telecommunication services. Such communication paths may connect telephone subscribers through a single switching system or connect them over long distances utilizing a number of switching systems and interconnecting transmission facilities. With the increase in special features provided by telecommunication systems, it is sometimes desirable to substitute one communication path between subscribers, which includes a special feature access, for a communication path which does not. For example, when two telephone subscribers wish to add other subscribers to a given conversation, a second communication path which includes conferencing arrangements may be substituted for the communication path originally connecting them. Typically, path substitution arrangements remove the old path and establish a new path between the subscribers without regard to continued path continuity. Such actions created noises on the line and periods during which no communication path exists. Both of these occurrences are potentially objectionable to telephone subscribers. With the advent of data communications, such loss of communication path continuity, or noise, has become an even greater problem. Additionally, when portions of each communication path may be controlled by different control entities, which is the case in present day distributed control switching systems, the coordination of effort to accomplish communication path substitutions severely complicates such activities.
A communication path substitution arrangement in accordance with the present invention eliminates, or substantially reduces, the service effecting difficulties of prior arrangements. Further, such an arrangement reduces the complexities involved in communication path substitution in distributed control telecommunication systems.